This invention relates to novel thiadiazole compounds and lubricant compositions thereof prepared from the derivatives of dimercaptothiadiazole and maleic anhydride or a halosuccinate. Lubricating compositions containing the compound, or their metal salts, provide antiwear and antioxidant properties.
Zinc dialkyldithiophosphates have been used in lubricants as antioxidant and antiwear additives for many years (CRC Handbook of Lubrication, CRC Press, Inc., 1984). However, there has been some concern regarding the presence of phosphorous-containing compounds in crankcase lubricants that may be harmful to automobile catalytic converters. It has been considered desirable to use non-phosphorous-containing additives that can provide comparable performance. The use of the derivatives of dimercaptothiadiazole, generally, in lubricants as inhibitors for corrosion and oxidation has also been long recognized (CRC Handbook of Lubrication, CRC Press, Inc., 1984). For instance, U.S. Pat. No. 4,193,882 also teaches that the reaction products of 1,3,4-thiadiazole and oleic acid inhibit metal corrosion.
According to the present invention, it has been found that the novel organosulfur compounds and their metal salts used as lubricant additives can inhibit oxidation and improve extreme pressure and antiwear characteristics of a lubricant. Zinc and molybdenum are preferred metal ions although other metals such as nickel, cobalt, iron, tin and antimony are useful.